1. Field of the Invention
The present invention relates to an electron microscope specimen and the preparing method thereof, and more particularly, to an electron microscope specimen which is suitable for constructing a three-dimensional image and the preparing method thereof.
2. Description of the Prior Art
With the miniaturization of semiconductor devices, the analysis techniques for observing the microstructure of semiconductor devices have become increasingly important. For example, the microstructure of the semiconductor devices can be observed by using a scanning electron microscopy (SEM) or a transmission electron microscopy (TEM). Due to the better resolution, TEM is widely used in analyzing semiconductor devices.
However, as the integration of semiconductor devices are upgrading and various semiconductor devices with special structure are proposed, current two-dimensional image analysis techniques are unable to reflect the device structure precisely, especially those devices with high curvature structure, for example, via structures. Therefore, the industry is developing a three-dimensional image technology which can retrieve two-dimensional (2D) images of the specimen from different angles and further construct a three-dimensional (3D) image out of the 2D images. Consequently, the real structure image of the product can be obtained.
Since the 3D image must be constructed by retrieving 2D images from different angles of the specimen, special configuration of the specimen is required. FIG. 1 and FIG. 2 are schematic diagrams showing the structure of the specimen for 3D image according to conventional art. As shown in FIG. 1, the specimen 100 includes a base portion 102 and a sample 104. The sample 104 protrudes from the base portion 102 to form a pillar structure. By using an electron beam 106 of the electron microscope, the wafer structure or microstructure of the sample 104 can be detected and observed. In order to retrieve the images from different angles, the specimen 100 is rotated along the axis in the direction of arrow A. Alternatively, as shown in FIG. 2, the specimen 100 can be tilted along the direction of arrow B between the angle α and the angle −α to collect more 2D images.
However, the conventional design of the base portion 102 and the sample 104 has an inherent limitation, which is also known as missing-wedge phenomenon. The missing-wedge phenomenon occurs, when the specimen 100, for example, is tilted beyond the angle α (usually 45 degrees). In such case, the images of the sample 104 cannot be captured by the electron microscope because the electron beam 106 is obstructed by the base portion 102, resulting in a nearly 45-degree missing wedge. As the thickness of the base portion 102 and the height of the sample 104 have both reached their critical values, it is difficult to overcome 45-degree threshold. Therefore, there is a strong need in this industry to provide an improved electron microscope specimen and the preparing method to resolve the above mentioned problems.